Phosphorus-Doped Polycrystalline Silicon via LPCVD: II. Surface Interactions of the Silane/Phosphine/Silicon System

Abstract

Secondary ion mass spectrometry (SIMS), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES) have been employed to study the interactions of silane (SiH4) and phosphine (PH3) with the Si(100) surface. Phosphine adsorption and desorption were investigated at surface temperatures in the range 25° ≤ T≤ 700°C. At ambient temperature, phosphine saturated the bare Si(100) surface after 3-5L exposure, and fitting adsorption data to a Langmuir model yields the values = 1.0 for the sticking coefficient. Phosphine adsorption was found to follow the 2 x 1 pattern of the underlying silicon. Competitive adsorption experiments set an upper bound of s ≤ 0.025 for silane adsorption under like conditions. The silicon surface was observed to be passivated with respect to silane adsorption by prior exposure to phosphine, with a layer of preferentially adsorbed phosphine formed which served to preclude subsequent silane adsorption. The results obtained here are discussed in the context of their bearing upon the phosphorus-doped low pressure chemical vapor deposition process. © 1984, The Electrochemical Society, Inc. All rights reserved.